Or is it just friction? Friction creating heat, just like an engine. I don't know, but I know airplane wings don't get hot. I'm just guessing here. It's not static. Static looks like the pic.

Static from a rotor wing is really colorful and pretty and I can't believe there aren't better pictures than this popping up on google images. I had a job in the army that had me standing under helicopters that were hovering so low I could touch them (they were that low so I could touch them), but I never took pictures.

That's static electricity in the picture. It has nothing whatsoever to do with sand. If you think rotor blades hit sand and that makes sparks or flashes of light or whatever, you're wrong. I would love to see actual scientific evidence that what you're claiming is even possible.

That's static electricity in the picture. It has nothing whatsoever to do with sand. If you think rotor blades hit sand and that makes sparks or flashes of light or whatever, you're wrong. I would love to see actual scientific evidence that what you're claiming is even possible.

In the middle of a desert, a military helicopter creates a stunning show while initiating an impossible static electrical discharge, spectacular phenomenon for all the lucky viewers of PDF....
[h=3]This is what exactly happens[/h]Helicopter RRPM is pretty much constant through out whether it be airborne or on the deck*When the aircraft is coming in to land/slowing down and is near to the ground, it tends to have a larger vertical downward component of air (induced flow) coming through the top of the disc being pushed out through the bottom (easily seen when landing in dust or sand). As the aircraft gets near to the ground, air is sucked up all around the aircraft (recirculation). In sandy or dusty areas, this too is sucked up around and then dragged back down through the disc. Most modern helicopter rotor blades are of a composite construction but usually tend to have a stainless steel or similar leading edge abrasion strip to help prevent wear to that part of the blade. The tip of the blade has the highest velocity and would tend to have the most amount of shit hitting it. Some theories suggest scintillation is caused by certain types of sand or dust (types with a higher ore or metallic content) striking the leading edge.One reason why you dont tend to see scintillation when an aircraft has landed is because even though the RRPM is pretty much still the same, we have no induced flow coming in through the top of the disc dragging or sucking the air (and any particles) in.As well as making the aircraft more visible to the enemy, there are issues of this bright glow around the disc affecting NVG (partially shutting them down at a fairly critical stage of flight!)
...

[h=3]Here’s the official US Army’s description:[/h]REDSTONE ARSENAL, Ala. — The “corona effect” is characterized by distinctive glowing rings along metal or fiberglass rotor blades operating in desert conditions.The glowing rings are made up of numerous small sparks resulting from grains of sand striking a normally-operating rotor blade, meaning the corona effect can be seen only at night.The corona effect has been seen from about a half mile away on a CH-47 Chinook hovering at about 1,700 feet, said Mike Hoffman, and that without the aid of night vision goggles.

What's crazy is that I never looked into that corona effect before, at least not reading about it, and now that I have I found bunk. That kid who claims there are pieces of metal flying off rotor blades has succeeded in spreading that disinformation across the entire web. I've stood under 1,000 helicopters, with a static discharge probe and rubber gloves, saw that halo 1,000 times, and I've never been in a desert.

One thing that kid completely made up was a metal covering for rotor blades. I read a bit of his site, and it seems like he's a creationist or something a bit crazy.

I always assumed it's static electricity, since helicopters generate a good deal of it, it has to be generated by the rotor blades and you get shocked when you touch a hovering helicopter. It happens all the time too.

The UK's Ministry of Defence is calling for research proposals on helicopter rotor blade scintillation.Scintillation, also known as 'the halo effect', occurs when particles stirred up by the rotor downwash interact with the blades. This is a particular problem in sandy or dusty environments. Little formal research has been conducted in this area, but possible causes include triboluminescence, chemiluminescence and electroluminescence.Proposals are sought to investigate the physics of this phenomenon and how to eliminate it.

Indeed they can be seen on civil turboprops too - the "silver" strip along the leading edge of a "black" blade - the blade is composite on a metal spar, and the leading edge is usually nickel alloy - one of the places I worked as a QA Engineer was a little maintenance outfit SAFE Air, in Blenheim New Zealand, who have a fairly large prop overhaul shop handling props from all around the Pacific. Replacement of these strips was "steady work".

All composite blades on aircraft require them because the composite material is too soft to withstand even "gentle" impacts.

Indeed - but shot blasting occurs at a much lower velocity than the ends of helicopter blades move at - shot blasting typically uses velocities of 65-110m/s, A Chinook blade tip, radius 9.15m, rotating at 225 rpm, does about 225m/s - twice the velocity, 4 times the potential impact.

also most shot blasting uses relatively soft shot in order to remove surface materials such as paint or loose materials such as corrosion, and so as to not damage the underlying strata. Shot that does seek to work the underlying material, such as for shot peening, is generally in the form of round particles, so as to "hammer" the material, not cut it.

the sand will probably have sharp edges and be very hard.

None of the leading edge materials make sparks.

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titanium and nickel can certainly spark - one of the ways of telling what metal something is made of is to grind it a little and see what sparks come off - titanium gives very hot white sparks, nickel gives dark red ones of short duration.

But also the static-inducing effects of particulates are very much stronger and permeate through all aspects of atmospheric interactions. I wonder how that helicopter would have appeared at night. Erupting volcanoes are very interesting in the dark.

justanairlinepilot said:

I'm assuming all items were grounded, that's why you didn't see any sparks.

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True. And the cabinets were well lit, which wouldn't have helped. But even at the time I was curious enough to look for it, as I expected some static to be there. Sometimes shot blasting was external to cabinets. But there again, Hampshire was a pretty damp place in the early sixties...

The pilot comes in fast, to the dark landing zone, lighted only by “Cyalumes,” which Americans call “Chemlights.” The sensitive camera and finely engineered glass make the dark landing zone appear far lighter. The apparent brightness of the small Cyalumes provides reference.

He's used a Canon 5d MkII, with some fast glass, $10,000 worth of gear. Possibly one that was modified:

2) Special Canon Mark II 5d (full spectrum): I had this one specially modified for shooting in low or zero ambient light. The sensor is sensitive to infrared and is “full spectrum.” It will pick up invisible IR lasers from rifles, Predators/Reapers (Taliban use cell phone cameras to see these lasers), IR sources, including the IR flash I had specially modified. This camera is in perfect condition but the body has dueling scars. This camera is also great for daylight. It will have the IR look and images are usually better with post-processing. Images with this camera can be phenomenal. Also good nighttime surveillance work. Various filters can make it useful for forensics, scientific, or astronomy work.

He also says

Content from external source

In motion, the halos spark, glitter and veritably crackle, but in still photos the halos appear more like intricate orbital bands.

So it would seem this is considerably different to how the scintillation would appear to the naked eye.

Yes, I gathered it was after dusk somewhat, but not using a special camera.

Particulates in fast moving air always generate static electricity. Hence explosions in coal mines and flour mills, or wherever the powder is combustible. The only way I know to rid that potential from a dusty area is to use that Evergreen jumbo to drop large amounts of water from above the area in advance of the helicopters. Cheaper than a million hippie ionizers?